The debt ceiling brawl, already bizarre and quasi-unhinged even by Washington standards, has just taken its sharpest turn into the surreal yet: Senate Democrats and the White House have agreed to offer Republicans a plan that by any standard the GOP could seize on to declare victory. And yet Republicans still won’t go for it.

Moments ago, Harry Reid formally unveiled his latest offer: $2.7 trillion in spending cuts, and no tax increases, coupled with a debt ceiling hike sufficent to give the Treasury authority to pay the U.S.’s obligations through the end of 2012. The plan also establishes a bipartisan committee to come up with future deficit reductions that would certainly put entitlements directly in its crosshairs, and would even guarantee a Congressional vote on its recommendations.

Though this gives Republicans everything they want while dropping any demand for new revenues, the White House just blasted out a statement endorsing Reid’s proposal: “Senator Reid’s plan is a reasonable approach that should receive the support of both parties, and we hope the House Republicans will agree to this plan so that America can avoid defaulting on our obligations for the first time in our history. The ball is in their court.”

By any measure, this would represent a clear win for Republicans. Yet rather than accept it, the House GOP is countering with its own proposal that would cut nearly $3 trillion and raise the debt ceiling — but it would happen in two steps. The GOP proposal would also create a commission to zero in on entitlements later.

Which prompted a good question from David Dayen: What exactly is the difference between the Reid and John Boehner proposals?

Both cut spending by similar amounts over time. Both raise the debt ceiling over time by roughly the same amount. Both virtually guarantee entitlements cuts later. Neither offers new revenues. It seems that perhaps the only meaningful difference between the two plans is that the Dem one gets it done in one fell swoop, while the GOP proposal does a short term deal followed by another one later — something that financial analysts say could lead to a downgrade of the U.S. credit rating and that Republicans themselves once opposed.

So how can Republicans oppose the Reid plan when it gives them virtually everything they want — it gives them more than twice as much in spending cuts up front than the Boehner plan does — while asking for nothing in the way of revenues in return? There are only three options that immediately come to mind. First: The GOP wants another debt ceiling fight closer to Obama’s reelection. Second: Even though Dems have given up on getting new revenues, a one-shot deal could help the president politically. Third: Republicans, having seen Dems concede multiple times already, see no reason not to drag us even closer to the brink in hopes of extracting still more. Perhaps GOP leaders think getting still more will make it easier to sell the compromise to a caucus that is now populated with a non-trivial number of public officials who are so delusional that they won’t raise the debt ceiling under any circumstances — even if Republicans are given 100 percent of what they want in return.

Maybe it’s a combination of all of the above, or maybe there’s some other reason GOP leaders haven’t divulged yet for opposing a plan that is a clear victory for them by any measure. Whatever it is, this debate has not just run off the rails; it’s sailing over the edge of a cliff, and it looks like our economy is about to follow.